Jonn Rippman is the national sales manager and training director for Blastrac. He has 24 years of experience in the surface preparation fields of grinding, cutting, scraping, shotblasting and polishing. For more details, visit www.blastrac.com.
An environmentally-friendly and cost-effective method to prepare asphalt, concrete and steel surfaces
For more than 35 years, shotblasting has been used in the industrial flooring market and on America’s roadways and bridges. However, many engineers and federal, state and local Department of Transportation (DOT) personnel have never seen the technology in action. Shotblasting is an alternative to diamond grinding, milling and open air blasting typically used to prepare roadways and bridge decks. Shotblasting has also been used instead of thin asphalt overlays and broadcast systems to increase tire-skid resistance.
What Is Shotblasting?
Shotblasting is a cost-effective and environmentally-friendly method for preparing asphalt, concrete and steel surfaces. This timesaving process strips, cleans and profiles the surface while leaving the resulting surface ready for chemical treatments, coatings and overlay materials.
Shotblasting can produce the International Concrete Repair Institute’s (ICRI) concrete surface profiles of CSP 3 through CSP 8.
Shotblasting produces excellent bonding characteristics that promote better adhesion and reduced coating failures.
How Does Shotblasting Work?
Shotblasting systems use a high-performance, airless, centrifugal or perimeter-fed blast wheel. In both types of wheels, kinetic energy charges steel shot by the blades on the rapidly rotating blast wheel, and the steel shot propels at a high velocity toward the surface. The shot strikes the surface and rebounds, and the shot and debris then enter an air-wash separator where the dirt and debris are separated from the shot.
The shot is recycled to the blast wheel repeatedly while the dirt and debris are transferred to the dust collector. This creates a steady blast of kinetic energy that strips laitance, coatings and surface contaminants while profiling the surface in one step. The dirt, dust and debris deposit in easy-to-handle bins or quick change-bags, reducing exposure to workers and the environment. During operation, shotblasting is virtually dust-free.
Different ICRI concrete surface profiles can be obtained by varying the shot size and travel speed. Selecting the shot size is critical to proper performance—the larger the abrasive, the larger the impact power, resulting in a larger profile. The smaller the abrasive, the less impact power, resulting in a smaller profile. A surface preparation specialist can help you select the correct abrasive size for a particular project or application.
What Are the Benefits?
Shotblasting does not require harsh chemicals or acids, and it does not necessitate containment. When used properly, little to no dust is emitted into the atmosphere, and the process has a minimal carbon footprint. The largest commercially available shotblast system consumes 28 gallons of diesel fuel and 1,000 pounds of steel abrasive to blast one lane-mile. This correlates to a carbon footprint of 0.543 tons per lane-mile. Compare this to 558 tons of carbon emissions to produce a lane-mile of asphalt and 2,408 tons of carbon emissions to produce a lane-mile of concrete freeway.
From a sustainability perspective, preserving roadways and bridges instead of replacing them makes sense. The low cost of shotblasting provides many benefits when compared to other pavement preservation methods. At a cost of roughly $6,680 per lane-mile, it costs one-twentieth the cost of asphalt repaving, one-third of the cost of chip seals and one-seventeenth the cost of a 2-inch asphalt overlay.
It also saves time and money by reducing material costs, labor and traffic control costs with shorter lane closure times. Shotblasting is the only process that has been proven to restore both micro and macro texture to asphalt and concrete roadways. This translates into higher skid resistance and safer roadways. If you couple shotblasting with available chemical treatments, the pavement life can be extended to five years, reducing the need to repave roadways.
To prepare concrete and asphalt surfaces for epoxy coatings, urethane coatings, MMA broadcast systems or polymer modified overlays, most manufacturers specify shotblasting as their preferred method of surface preparation. It produces a clean profiled substrate in one pass with no chemicals or water. No additional time is needed for the substrate to dry.
The product can be applied once the surface is blasted, which means less lane closure time and a faster return to service. It eliminates drying time and costly and time-consuming disposal methods associated with other surface preparation methods. The production rate, finish profile and low operating cost make shotblasting an important tool to help maintain, repair and restore the world’s infrastructure system of roadways, airports and bridges.
Construction Business Owner, May 2012